The present invention concerns communication cables using optical fibres to convey information in a very wide frequency band. The use of optical fibres as guides to propagate optical wave modulated by the information to be transmitted is tending to increase and, although it is curbed by the cost of the fibres themselves, it is reasonable to expect that industrial progress to occur in the next few years will permit such reduction in the cost of the fibres that the cables with optical waveguide will be competitive with copper high capacity and high quality cables.
The use of optical fibres presents new problems to cable manufacturers owing to the fragility of the fibres and the sensitivity of their transmission characteristics to mechanical stresses.
The present invention relates to a cable element structure comprising optical fibres which can be cabled by standard cable making machines currently used for standard cables. Such a structure shows the economical interest of manufacturing optical fibre cables with available cable making machinery without further investment.
United States Patent application Ser. No. 877,872 filed on Feb. 15, 1978 for: "Cable incorporating optical fibres" discloses a cable element which comprises a core consisting of one or more wires of mechanically rigid material, of which the elongation is greater than that of the material of the optical fibre and on which dielectric is extruded. The surface is formed with a set of helical grooves for lodging optical fibres and the outward opening of the grooves is at least partially closed by lips so as to prevent the dislodgement of the fibre and to protect it from any contact during subsequent cable making steps. The present invention is applicable to such an element and also to simplified grooved structures without lips.